Eerie glow on ocean floor baffles scientists

Keay Davidson, EXAMINER SCIENCE WRITER

Published 4:00 am, Sunday, October 6, 1996

An eerie and unexplained light on the ocean floor is tantalizing scientists.

Researchers from astronomers to biologists to physicists are debating numerous theories to explain the strange glow. It's too dim to be perceived by the human eye but has been recorded by super-sensitive cameras aboard Alvin, the famed miniature research submarine.

The glow illuminates the nearly pitch-black sea floor along the edges of newborn ocean crust just off the coasts of the Western United States and Mexico and in the mid-Atlantic.

Theories range from the mundane - that the light glows for the same reason a hot stove does - to the fanciful - the glow may come from the same source as sparks that burst from a popular hard candy when you chomp it - to the exotic - that the light glows because of popping bubbles in a process that might someday generate nuclear fusion energy.

A few theories are so daring that, if verified, they would transform our understanding of the origin of life and one of nature's prime biological processes - photosynthesis, by which sunlight and chemicals produce the oxygen we breathe, the plants we eat and the vast green lushness of nature.

Scientists have always assumed photosynthesis is restricted to Earth's surface; after all, that's where the sunlight falls. But the glow might provide the ocean bottom with a second, far weaker "sun" able to power undersea photosynthesis and, thereby, to nourish weird life such as shrimp without eyes.

"It would be a tremendous discovery to find photosynthetic organisms down at those (undersea volcanic) vents - I would be ecstatic," says Professor Robert Blankenship, who got his doctorate at UC-Berkeley and now works at Arizona State University.

Although "blind" in the ordinary sense of the word, a type of sea floor shrimp - Rimicaris exoculata - has light-sensitive cells on its back. Scientists theorize the shrimp might "see" the glow via the cells. The glow might allow the creatures to sense whether they're too close to the super-hot volcanic vents, where they would end up as boiled shrimp.

The glow has been detected at thermal vents in three areas of the world's oceans where hot lava oozes through volcanic or "hydrothermal" vents to the surface, forming new crust.

The sites include the "Endeavour Hydrothermal Fields" along the Juan de Fuca ridge off the Pacific Northwest coast; the East Pacific Rise off Baja California; and the Mid-Atlantic Ridge, which runs down the middle of the Atlantic Ocean like a seam in a baseball.

First observed in the late 1980s, the glow has proven astonishingly resistant to explanation. Some scientists assumed the glow was an ordinary form of light generated by heat from volcanic vents. A familiar form of this

"thermal radiation" is the reddish glow of a hot stove.

But a new study probably has shot down the idea, leaving scientists flummoxed.

As it turns out, the light is brighter away from the volcanic vents, which continually spew new ocean crust, than right next to them, as the thermal radiation theory would suggest, marine biologist Cindy Lee Van Dover of the University of Alaska at Fairbanks and three colleagues report in a recent issue of Geophysical Research Letters. The glow also emits far too much red and infrared light to be purely thermal radiation.

The glow is so faint that the scientists have been forced to "photograph" it with a special electronic camera. Such charge-coupled devices, or CCDs, are normally used to detect photons of light from the dimmest and most distant of galaxies in outer space.

The camera sits within a super-secure container to prevent it from being crushed by the pressure of water thousands of feet deep.

With two or three people crammed aboard, the yellowish, bug-eyed Alvin - familiar to PBS viewers from countless National Geographic specials - drops from a ship toward the dark sea bottom.

Thousands of feet down, the pilot switches on the headlights and faces an otherworldly realm. Forests of tall, spire-shaped rocks loom over fuming "black smokers" : volcanic vents that gush black chemicals "a lot like a fire hydrant," Van Dover says. In 1988, while working with John Delaney of the University of Washington at Seattle, she first saw the undersea glow.

"If you turn the lights off and turn on the CCD for a 40-second exposure," Tyson says, "what you see is a very faint glow.

"At a distance it looks like green light. . . . Except the closer one gets to it, the redder it gets."

Some speculate that photosynthesis might have started on Earth when undersea organisms learned how to exploit the faint glow to create energy and food. Later, early plants and creatures might have moved from the ocean into the atmosphere, and thereby photosynthesis shifted its dependence from the deep-sea glow to the sun. Plants convert solar energy into chemical energy that drives their growth and generates oxygen, one of the two main constituents of our atmosphere.

What is the glow? Theories abound. They include:

*Triboluminescence. An everyday example is Life Savers Wint-O-Green candy: "Go into a dark room and bite on it, and there's a flash of light," Tyson says. The phenomenon occurs when high pressure causes crystals in the candy to emit photons of light.

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*Crystalloluminescence. As the super-hot, salty water cools, it might condense into crystals that emit photons.

*Sonoluminescence. Sound waves cause bubbles to collapse. As they do, they emit light. On a future Alvin dive, the researchers will take a hypersensitive microphone in hopes of "hearing" the bubbles collapsing. In unrelated research, Lawrence Livermore National Laboratory scientists have explored the possibility of using sonoluminescence to generate nuclear fusion energy in liquids.&lt;

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